The Internet of Things (IOT) is a network on which information about a physical world is obtained by deploying various devices having specific perception, computing, execution, and communication capabilities, and that is used to implement an interconnection between a person and an object and between objects by means of information transmission, coordination, and processing. In short, the Internet of Things is used to implement interworking between a person and an object and between objects. Possible applications of the Internet of Things include various aspects such as a smart grid, intelligent agriculture, intelligent transportation, and environment detection.
As a mobile communication standardization organization, the 3rd Generation Partnership Project (3GPP) is conducting technical research and standard optimization for Internet of Things services. A main research and optimization direction is to implement cost reduction and coverage enhancement. In terms of cost reduction, an operating bandwidth of a terminal device can be reduced. For example, limiting an operating bandwidth of a terminal device to 1.4 MHz (or 200 kHz, or 180 kHz) is an important research direction. In terms of coverage enhancement, coverage enhancement support is provided mainly for a machine type communication (MTC) device having a relatively large path loss in places such as a basement, so that the device in a special scenario can access a network to obtain a service. Coverage enhancement means providing coverage enhancement support for terminal device having a relatively large path loss in places such as a basement and a cell edge, so that the terminal device in the foregoing scenarios can access a network to obtain a service. Coverage enhancement may be implemented in one or more of repeated transmission, spread spectrum transmission, retransmission, transmission time interval bundling-based transmission, narrowband (for example, subcarrier scheduling) transmission, ultra-narrowband (whose bandwidth is, for example, dozens of hertz to more than 10 kilohertz) transmission, power spectrum density boosting-based transmission, requirement relaxed transmission, or continuously attempted transmission. Signal repetition is one of methods for implementing coverage enhancement. When coverage enhancement is implemented, coverage can be expanded to some extent, but more system resources may be consumed. Therefore, it is necessary to improve resource utilization when signal repetition is used to implement coverage enhancement.
Communication between a base station and terminal device may be implemented in one of a plurality of communication modes. For example, a plurality of communication modes are supported in a transmission bandwidth of a legacy carrier. A communication mode may be understood as an air interface communications technology, a communications specification, a communication deployment scenario, or a communications standard. Different communication modes may be understood as different air interface communications technologies, different communications standard technologies, or the like. For example, terminal device in a Long Term Evolution (LTE) system or a Long Term Evolution Advanced (LTE-A) system supports an LTE (or LTE-A) communications technology. A base station can further communicate with another terminal device (for example, MTC terminal device or IoT terminal device) on an LTE carrier by using another air interface technology different from an LTE communication mode.
Therefore, when a base station and terminal device communicate with each other, communication between the base station and the terminal device may be implemented in one of a plurality of communication modes (for example, one of two, three, or more types of communication modes). However, an existing indication method is applicable only to indication of a frame structure, information content, and the like, and there is no method for indicating a communication mode in the prior art.